This invention relates generally to an automatic soldering apparatus and, more particularly, the present invention is concerned with an apparatus for uniformly applying molten solder to printed circuit boards carrying electrical parts thereon by dip soldering or touch soldering.
There have thus far been proposed various apparatuses of a conveyorized type for automatically soldering printed circuit boards by means of dip soldering. However, the conventional machines have a tendency to give rise to problems of soldering failures especially when applied to printed circuit boards whose underside surfaces have recessed or concaved portions. Such recesses can block the molten solder from flowing thereinto and can trap gases therein, causing incomplete deposition of the solder. The air bubbles which are once trapped in the recesses are difficult to remove even if the printed circuit board is contacted with molten solder for a long period of time.